Device for transforming a digital signal into an acoustic one, and that makes use of a standard phase modulation

ABSTRACT

A device for transforming a digital signal into an acoustic signal, making use of a standard phase modulation, that comprises a modem chip ( 1 ) with a phase modulation of known kind, used until now for the data transmission via cable, conceived and used only for a cable connection, for acquiring a digital signal through a serial inlet RS232 and for modulating the same according to a standard record V.22, and an acoustic transducer ( 2 ) of the piezoelectric kind guided by the modem chip ( 1 ).

The present invention concerns a device that transforms a digital signal into an acoustic signal, making use of a standard phase modulation, and having the purpose of transmitting data through a fix or mobile/cellular telephone line.

It is well known that, at present, the transmission of data through acoustic coupling, performed e.g. with a common telephone, has become a quite simple operation, in particular when a standard record is used. However, the known art sets unavoidable limits for making use of said system the reliance whereof remains in any case low. The limits derive from two critical points the technique has not yet been able to overcome:

-   -   the need of a perfect alignment between transmitter and receiver         (telephone). In fact, when said alignment is not perfect, the         data transmission shows a high percentage of error, as it also         happens when the two surfaces are not in perfect contact one         with the other.     -   high sensibility to acoustic noise (surrounding) and to         vibrations. During transmission it is necessary to remain silent         and reduce (or eliminate wherever possible) the surrounding         noise because it may alter the acoustic signal to be         transmitted.

The need derives from above described situation to adopt special precautions for reducing above mentioned inconveniences to the minimum, whereby they can never be completely eliminated. Some of the devices used for said purpose are listed herein below:

a. rubber bands, or similar accessories, for fixing the transmitter and the receiver so as to assure a better mechanical coupling. In particular, the transmitted must be coupled with the microphone of the telephone receiver, for receiving and consequently transmitting on the telephone line.

b. gaskets, adapters, supports etc. for assuring the sealing between the transmitter and the telephone, in consideration of the great variety of possible shapes of the latter. In fact, some “particular” telephone shapes (especially of the microphone) may even make the coupling impossible. Just think of a telephone with a modem design in which the receiver has a design in the shape of a point, like a pyramid.

c. the so-called acoustic cloth puts between the transmitter and the telephone so as to attenuate the vibrations between the two “machine bodies”, which are a sure source of transmission errors.

As far as the kind of modulation used, there exist different modulation techniques, which are characterized in the modulation records used, in error probabilities and transmission speed. There are, e.g., two kinds of modulation used also for the transmission of data through the telephone line:

-   -   frequency modulation (FSK)     -   phase modulation (PSK).

The frequency modulation (FSK) is the one mostly used for transmitting data through an acoustic coupling; it shows the advantage of not being owner and to be able to use a common standard modem; on the other side, it has a low efficiency in terms of relationship signal/noise at equal transmission speed towards other modulation techniques.

The phase modulation (PSK) is a rather efficient modulation technique which allows, in theory, the data transmission at extremely high speed or, if used at a relatively low speed, with an extremely high efficiency. Due to this latter feature, it is widely used for low speed cable transmissions, where a great safety in the data transmission is required (e.g. counters for automatic drawing). Today, the phase modulation is used for the data transmission without cable only in a few cases in which a special owner record has been developed for the acoustic coupling. This implies the disadvantage that, for receiving, a non standard modem must be used that needs, for entering the net, a special approval for the telephone lines o each single Country and this is a limit that slows down the commercial development thereof. Even in the case of an acoustic coupling realized with a phase modulation and a non standard modem, the present art has not been able to solve the above mentioned inconveniences (the need of a perfect alignment between microphone and transducer and the high surrounding noise sensibility).

It is the aim of the present invention to overcome above mentioned inconveniences by means of a device able to transform a digital signal into an acoustic signal making use of a standard phase modulation, conceived so as to be inserted into a system for the transmission of digital signals via telephone by means of a simple acoustic coupling, shown in a block scheme in FIGS. 1 and 2, in the two data transmission variants through a fix telephone and through a cellular telephone.

FIG. 1 shows a device that transforms a digital signal into an acoustic signal, making use of a standard phase modulation, and the functioning block scheme works through a fix telephone line, consisting of:

-   -   a modem chip 1 with a phase modulation of known kind, used until         now for the data transmission via cable, conceived and used only         for a cable connection for acquiring a digital signal through a         serial inlet RS232 and for modulating the same according to a         standard record V.22;     -   an acoustic transducer 2 of the piezoelectric kind guided by         said modem chip 1;     -   a feeding and connecting circuit.

The transmission block T shown in FIG. 1 comprises a telephone apparatus TF with a microphone M that can be reached by an acoustic signal SA, and a telephone line LT connects the same to the receiving block BR consisting of a standard modem MS for the outlet of a digital data signal SD.

For what concerns the variant of FIG. 2, the transmission block T comprises, instead of the telephone apparatus TF, a mobile telephone apparatus TFM which, through the repeater R, is connected by means of the telephone line LT to the receiving block BR.

The present invention provides the use of the standard phase modulation instead of the frequency modulation commonly used for the transmission of data of acoustic kind. This has been made possible making use of a modem chip (that males use of the standard record V.22) available on the market but, as mentioned above, conceived and used only for a cable connection.

The advantages of the device according to the present invention are many and considerable:

-   -   the inconveniences and the respective limits of the actual         method are completely overcome and, consequently, it is made         possible to perform the transmission in conditions that would be         considered impossible according to the present knowledge and         that correspond to the situation of simple nearing between         transmitter and receiver;     -   the device allows a reliable data transmission through a         telephone line under the following acoustic coupling conditions,         where no other similar data transmission device could succeed:         -   the transducer and the microphone are physically far away,             until a distance of one meter;         -   the transducer and the microphone are not aligned (within a             distance of one meter);         -   the orientation of the operation fields of the transducer             and of the microphone is diverging, as—e.g.—in the situation             in which they are both resting on a plane with opposed             orientation;     -   the device according to the present invention allows a reliable         data transmission through a telephone line under the following         acoustic coupling conditions:         -   a high surrounding noise during transmission;         -   a telephone apparatus with an irregular shape that does not             allow a perfect adherence of the microphone with the             transducer.         -   Under such conditions, any other similar device for the data             transmission would succeed only with a considerably lower or             very low reliability degree.     -   the device makes use of the phase modulation of the signal and         due to the high efficiency that may be obtained from the latter,         it guides an acoustic transducer (a piezoelectric buzzer) of         extreme simplicity and extremely low used power (in the range of         one micro-watt), instead of a more expensive loudspeaker of the         electromagnetic kind. This implies further advantages in terms         of costs, lightness/encumbrance and an extremely low electric         current consumption (fundamental in a battery-fed         pocket-system);     -   due to the extremely low power used by the device, a greater         autonomy of the batteries is obtained: with the same autonomy         batteries (or even rechargeable batteries) of lower capacity may         be used with advantages, also in this case, in terms of cost,         lightness and encumbrance.

Such advantages are particularly important when considering the industrial usefulness of the device according to the present invention, especially relating to mobile devices of tele-medicine.

It appears evident how, due to the device according to the present invention, the cable-less data transmission by acoustic coupling through a common telephone apparatus may become a simple and extremely reliable method if considered to what is available at present.

Due to the reliability obtained, it will be possible to suggest the new system in all situations providing great diffusion, e.g. also for transmitting data in a “tele-medicine” service which thus will become available even to old people with reduced psychomotor capacities or not completely self-sufficient. 

1. A device for transforming a digital signal into an acoustic signal, making use of a standard phase modulation, characterized in: a modem chip (1) with a phase modulation of known kind, used until now for the data transmission via cable, conceived and used only for a cable connection, for acquiring a digital signal through a serial inlet RS232 and for modulating the same according to a standard record V.22; an acoustic transducer (2) of the piezoelectric kind guided by said modem chip (1); a feeding and connecting circuit, and making use of a standard phase modulation instead of the frequency modulation commonly used for the data transmission of acoustic kind.
 2. A device according to claim 1, characterized in that it makes use of the phase modulation of the signal and due to the high efficiency that may be obtained by the latter, guiding an extremely simple acoustic transducer (piezoelectric buzzer) at very low power (in terms of one micro-watt), instead of a more expensive loudspeaker of the electromagnetic kind.
 3. A device according to claim 1, characterized in a reliable data transmission through a telephone line under the following acoustic coupling, where no other similar data transmission device would succeed: the transducer and the microphone are physically far away, until a distance of one meter; the transducer and the microphone are not aligned (within a distance of one meter); the orientation of the operation fields of the transducer and of the microphone is diverging, as—e.g.—in the situation in which they are both resting on a plane with opposed orientation. 